1. Field of the Invention
This invention relates to vehicle drive controls and in particular to such controls utilizing a single manually operable control lever for effecting selective steering drive of a vehicle.
2. Description of the Prior Art
In one conventional form of vehicle, commonly known as a crawler vehicle, hydrostatic drive systems are provided whereby left and right side crawler tracks are selectively driven to provide a desired steering drive of the vehicle. The steering control means is provided adjacent the driver's seat and is connected to the drive systems by conventional push-pull linkages responsive to movement of the control by the driver to effect the desired steering drive of the vehicle.
The present controls for effecting such steering drive are relatively complex and costly. Because of the complexity, at times, confusion arises in the use of the control in attempting to steeringly drive the vehicle therewith.
One example of a prior art control mechanism for use in controlling the drive of self-laying tracks of crawler-type tractors, is illustrated in U.S. Pat. No. 3,181,389 of Paul P. Richard. As shown therein, a vehicle drive control is provided including two parallel plates provided with arcuate slideways parallel to each other and receiving a slider adapted to be shifted along the slideway and carried on connecting rods. The steering of the tractor is obtained by shifting the ends of the connecting rods along their slideways. The connecting rods have a length such that pivotal movement of the rods with respect to the levers causes the rods at their ends supporting the sliders to generate arcs passing through the axis of the spindle and lying parallel to the arcuate slideways. This arrangement makes it possible to selectively make the slideway system turn without any modification in the relative position of the ends of the connecting rods with reference to the slideways, or else to shift either or both ends of the connecting rod with reference to the corresponding slideways and thereby effect a desired control of the tractor drive means.
In U.S. Pat. No. 3,295,391 of Wolfgang Ernest et al, a locking means for a lever-operated multi-position valve device is shown comprising a lever-operated multi-position control valve device. For actuating the valve actuators of the three valves controlled by the device, three integral arm members extend radially and perpendicularly from a central cylindrical operating handle member, with each of the arm members, including near its outer end, a socket member threadedly received in a through bore in the respective arms and being releasably lockable in any axial position by means of a nut. A combined ball and rod member is disposed for universal movement between each socket member and the corresponding one of the valve actuators so that movement of the shaft about either or both of the pivot pin and shaft for the control operation effects a corresponding downward movement of a valve actuator to effect operation of the corresponding valve device.
Gianni Scolari, in U.S. Pat. No. 3,620,096, shows a single maneuvering level control for tracked vehicles for controlling the delivery of hydraulic fluid of variable feed pumps in track vehicles permitting controlling both tracks of a track vehicle by a single manually operable lever. The maneuvering lever includes a lower section pivotable at its lower end along a horizontal axis and an upper section pivotably mounted on the upper end of the lower section. The upper section is mounted for rotation along an axis orthogonal to the horizontal axis. Means are provided for connecting the upper section to a rocker having arms connected to the delivery regulators of the hydraulic pumps.